Need serious rethinking on the use of Zinc-EDTA or other chelates for plant nutrition - Bio-chemical issues

Need serious rethinking on the use of Zinc-EDTA or other chelates for plant nutrition - Bio-chemical issues

I think the scientific community – agriculturalists, biochemists, plant physiologists, fertilizer specialists – need to give serious thought to the use of micronutrient chelates as a source of micronutrient nutrition for crops.

There are several fundamental questions that raise doubts on how chelates can ever be considered as a nutrient carrier.

I would say the fundamental issues are the following :

1.     Taking Zn-EDTA as an example, Zn from this chelate can be used to produce plant proteins or enzymes if and only if  the plant protein / enzyme can remove the Zn ion from its tight binding with EDTA – i.e., the forward reaction

Zn-EDTA + Protein -> Zn-protein + EDTA

must occur. By chemical laws, this can occur only when the dissociation constant of Zn-protein is lower than the dissociation constant of Zn-EDTA (i.e., only if the Zn-protein binding is tighter than the Zn-EDTA binding).  The dissociation constant of Zn-EDTA is around 10^-16 M whereas zinc containing metalloproteins have way below this (at around 10^-9 M to 10^-12 M). What this means is that through the plant would have Zn as Zn-EDTA circulating within its system, that Zn would not be ‘useful’ Zn – it cannot be used to synthesise biochemical proteins.

2.     Even if some proteins did extract the Zn from the Zn-EDTA then there would be free EDTA circulating within the cells & that would make matters even worse. The EDTA would bind to any other metal ion like Fe and cause further damage.

3.     Tissue analysis would indicate ‘sufficiency’ of zinc but that is all in a useless form.

4.     EDTA as a carrier is never recommended for animal nutrition – why? Simply for the same reason that the chelated form that goes in will be of no use in biochemical synthesis of essential proteins. In fact EDTA is used as a treatment for removing toxic levels of metals from the human / animal body.

In summary the point is this :- if the science behind a process is not correct how do we recommend its widespread use? 

We really need to look into this deeply!

Field testing of micronutrient fertilizers

How to get a reliable field test of micronutrient fertilizers :

Testing of micronutrient fertilizers is particularly sensitive because yield differences may be narrow. Therefore, avoidable errors must be kept low if yield responses are to be analyzed at 5% probability level. Large scale testing is not suitable for yield potential evaluation. Though protocols vary with the nature of material being tested, some minimum requirements must definitely be followed. This includes (i) maintaining equal populations in all test plots, (ii) equalizing N, P, K, S and Mg applications in all plots, (iii) accurate weighing of fertilizers for each individual plot and (iii) careful harvesting and accurate weighing of produce.

Nutrient release by Smart Micronutrients

Is nutrient release dependent on soil / environment / crop?

Since the dissolution reaction is triggered by the plant, environmental factors do not affect nutrient availability. So as long as the environment allows the plant to grow and survive, plants will be able to uptake the nutrients according to their needs. The key here is that Smart Micros do not require environment triggers for nutrient release but only an actively growing plant. Rate of release is dependent only on rate of plant growth.

Is the nutrient release driven by low pH or is there a selectivity to specific types of acids?

   Soil pH has no effect on nutrient release. The effect of root acids is mainly due to the chelating action (if these acids were neutralized to >pH 7 the Smart Micros would still dissolve). However, the molecules do dissolve by acids alone but that is at very low pH levels (pH<2) that are not present in soils. So, effectively, release in soils is only due to chelating action and not due to acid induced dissolution.

What causes the plant to release these acids that release in turn the micro-nutrients? Is this release related to growth?

Exudation of various acids and enzymes is a natural process in plants and the means by which plants are able to utilize the nutrients bound to the soil matrix. This release is related to growth (because the plants’ requirement of nutrient increases with growth) and plant roots proliferate as the plant grows. There is also increased secretion of exudates when the plant experiences deficiency of a nutrient (it is an intelligent feed-back mechanism so that the plant secretes more in order to take up more nutrient when there is a greater need).

Field trials with Smart Micronutrients

SUMMARY OF FIELD TRIALS WITH SMART MICRONUTRIENTS

CROP	FERTILIZER	MICRONUTRIENT FERTILIZER dosage	Yield increase	% yield increase over control
Rice	Smart zinc	0.5 kg/ha Zn	768 kg/ha	19.4 %
	Zinc sulfate	5 kg/ha	233 kg/ha	5.9%
Rice	Smart zinc	0.5 kg/ha Zn	1288 kg/ha	23%
	Zinc sulfate	5 kg/ha	Nil	Nil
Peanut	Smart zinc	0.6 kg/ha	860 kg/ha	36.2%
	Zinc sulfate	5 kg/ha	124 kg/ha	5.2%
Corn	Smart zinc	0.75 kg/ha	927	9.1%
	Zinc sulfate	4 kg/ha	317	3.1%
Cabbage	Smart zinc-iron-manganese-copper-boron	Zn-Fe-Mn-Cu-B (0.75-0.38-0.19-0.19-0.09 kg/ha)	6150 kg/ha	12%
	Zinc-iron-manganese-copper sulfates-borax	Zn-Fe-Mn-Cu-B (4-2-1-1-0.5kg/ha)	255 kg/ha	0.5%
Potato	Smart zinc-iron-manganese	Zn-Fe-Mn (0.75-0.375-0.187 kg/ha)	1365 kg/ha	24%
	Zinc-iron-manganese sulfates	Zn-Fe-Mn   (2-1-0.5 kg/ha)	190 kg/ha	3.3%
Red cabbage	Smart zinc-iron-manganese-copper	Zn-Fe-Mn-Cu  (0.75 - 0.375-0.19- 0.09 kg/ha)	6475  kg/ha	14.3 %
	Zinc-iron-manganese-copper sulfates	Zn-Fe-Mn-Cu  (0.75 - 0.375-0.19- 0.09 kg/ha)	428 kg/ha	1%
Red Lentil	Smart zinc-iron-manganese-molybdenum	Zn-Fe-Mn-Mo (0.5-1-0.5-0.04 kg/ha)	244 kg/ha	17%
	Zinc-iron-manganese-sulfates Ammonium molybdate	Zn-Fe-Mn-Mo  (0.5-1-0.5-0.04 kg/ha)	Nil	Nil
Black gram	Smart iron-manganese	Fe-Mn   (1-0.5 kg/ha)	422 kg/ha	28.2%
	Iron-manganese sulfate	Fe-Mn (4-2 kg/ha)	147 kg/ha	9.8%
Green gram	Smart zinc	0.5 kg/ha Zn	126 kg/ha	12%
	Zinc sulfate	5 kg/ha Zn	61 kg/ha	5.8%

Formulations

Versatility in formulations with macronutrient fertilizers :

Because Smart micronutrients are non-reactive there is complete versatility in the ways in which they can be combined with bulk fertilizers. This is property is unique to Smart and, therefore, the potential uses of Smart in formulations is vast.

(a)   In granulation with NPK fertilizers : Conventional micronutrient fertilizers (sulphates and chelates) are not suitable for use in granulation with NPK fertilizers because they react and alter their chemical state into forms that are ineffective. The major advantage of the Smart micronutrients is that they can be granulated with any of the NPK fertilizers including SSP, TSP, DAP, etc. They are non-reactive to the bulk fertilizer and retain their unique properties. Thereby each granule is consistently uniform in composition, each granule delivers micronutrients and there is a much more effective dispersion of the micronutrient in soil.

(b)   Coating on NPKs : Smart can be readily coated on to bulk fertilizer granules.  The powdery micronutrients are easily amenable to coating and retain their effectiveness.

Benefits of Smart Micronutrients

Benefits of Smart Micronutrients

• The fertilizers are non-polluting; unlike existing fertilizers, these water insoluble fertilizers will not pollute ground water.

• Solves the problem where nutrient release and crop requirements may not match.  In this fertilizer nutrient release is biological (by root organic acids, therefore plants can solubilise and take up the nutrients whenever they require.  In other slow release formulations, nutrient release is controlled by hydrolysis or diffusion causing the crop requirement nutrient release mismatch problem.

• Crop yields increase by 10-30% and are higher than with water soluble micronutrients

• High cost-benefit ratios of 5:1

• Storehouse of continuous nutrient source throughout the crop growth period.

Disadvantages of micronutrient sulfates and chelates

Micronutrient sulfates & chelates are water soluble fertilizers

Water soluble fertilizers are subject to leaching, drainage causing -

          > Water & air pollution.

          > High wastage of nutrients.

Nutrients become non-available over time due to soil fixation requiring -

         > Excess dosage and frequent applications of fertilizers.

Mismatch between plant requirement & nutrient availability because -

         >  Crop nutrient requirements vary during growth period.

         > Current fertilizer applications result in feeding through a fire-hose. 

         > Either over nourishment or deprivation of key nutrients during plant growth cycle.

Introduction of undesirable components -

        > Soil acidification

        > Accumulation non-biodegradable compounds. EDTA is non-biodegradable & a serious                      pollutant of water

Introduction to Smart Micronutrients

Introduction to Smart Micronutrient technology :

Our “SMART MICRO” technology has introduced a unique concept in fertilizers. This concept for fertilization is the first in the world. 

We design molecules so that they >99% water insoluble but >99% soluble in plant secreted acids through a nutrient release mechanism that is activated by plant root activity. This new nutrient delivery mechanism ensures that the plant gets whatever amount of nutrient it wants at any time it needs it.

The solution is in developing the molecular structure in such a way that it will not dissolve in water but will dissolve in the organics that are secreted by plant roots. Thus the raw materials are all plant 'digestible' food. These compounds serve as miniature stores from which the plant can access the nutrient according to its needs.

Deeper look at how this works :

Release of nutrients from Smart Micros, utilizes the plants’ own mechanism of releasing insoluble micronutrients from the soil matrix. Soils do not contain any significant water soluble micronutrients – they are all bound to the matrix. Roots release various organic molecules (enzymes, phytosiderophores, etc) which chelate the insoluble micros and bring them into solution for further uptake by the plant. (The process is similar to the way in which the digestive systems in humans, is able to solubilize and absorb insoluble foods). This is the usual way in which plant roots are able to dissolve and ‘digest’ nutrients present in insoluble forms in the soil. However, not all insoluble can be ‘digested’ by plant roots. So our approach is to make the insoluble molecules with a certain molecular structure that would allow it to dissolve in root exudates.